Toothbrush

Abstract

A toothbrush including a brush main body of a synthetic resin and having a bristle base and bristles of a thermoplastic resin which have been fusion-bonded to the bristle base to constitute a bristled part, the bristles constituting the bristled part at least partly comprise: tapered bristles which are bristles having split free ends, the split free ends having been tapered beforehand; tapered bristles which have a sectional shape having a core-sheath structure or islands in a sea structure; or tapered bristles in each of which a core bristle comprising a core or island part has been formed beforehand so as to be exposed at the free end. The toothbrush has excellent suitability for bristle insertion into narrow parts. It is highly effective in removing dental plaque and cleaning the teeth. It is highly easy to use in the oral cavity. It further has a highly attractive appearance.

1. A method for manufacturing a toothbrush with the following steps:
 (a) providing bristles made of a thermoplastic resin; 
 (b) wherein at least some of the bristles comprise tapered bristles with a sectional shape having an islands in a sea structure wherein a core bristle having a plurality of island portions exposed beforehand at a free end, and 
 (c) subsequently inserting a tuft comprising a plurality of the bristles into tufts holding holes formed in a first mold member from a front end side of the bristles against an opposite side from a cavity side, then bringing a free end portion of the tuft in contact with a backplate, setting a brushing surface formed by end portions of the bristles at a predetermined shape, heat melting a base end of the tuft to form a thick portion comprising a fused mass at the base end of the tuft, then mounting the thick portion in such that the tuft is fusion-bonded to a bristle base, and forming a brush main body made of a synthetic resin with the bristle base in molds. 
 
     
     
       2. The method according to  claim 1 ,
 wherein the bristle base is not more than 4.0 mm thick. 
 
     
     
       3. The method according to  claim 1 ,
 wherein each of the tapered bristles are synthetic resin filaments each with a sectional shape composed of a plurality of connected unit cross-sectional elements. 
 
     
     
       4. The method according to  claim 1 ,
 wherein each of the tapered bristles is formed in a tapered shape in which the sheath portion or sea portion becomes thinner towards the free end and is a split bristle with a plurality of core bristles exposed at the free end. 
 
     
     
       5. The method according to  claim 1 ,
 wherein each of the tapered bristles is formed in a tapered shape in which the sheath portion or sea portion becomes thinner towards the free end and is a tapered bristle with a single core bristle exposed at the free end. 
 
     
     
       6. The method according to  claim 5 ,
 wherein the cross-sectional shape of each of the core bristles of the tapered bristles exposed at the free end has a nearly same shape throughout the length in the axial direction of the core bristle. 
 
     
     
       7. The method according to  claim 1 ,
 wherein each of the bristles is made of a material containing at least one kind of thermoplastic resin selected from polyester resin, polyamide resin, and polyolefin resin. 
 
     
     
       8. The method according to  claim 1 ,
 wherein in each of the tapered bristles, a main component of the material of the core or island is a polyamide resin, and a main component of the material of the sheath or sea portion is a polyester resin. 
 
     
     
       9. The method according to  claim 1 ,
 wherein the bristled part comprises at least two or more kinds of bristles of different specifications. 
 
     
     
       10. The method according to  claim 9 ,
 wherein the bristled part is formed by implanting at least two or more kinds of tapered bristles of different specifications. 
 
     
     
       11. The method according to  claim 1 , wherein the tapered bristles are implanted to at least part of a front end portion, right-side surface portion, center portion, left-side surface portion, and rear end portion of the bristled part. 
     
     
       12. The method according to  claim 1 ,
 wherein a brush surface composed of the free ends of the bristles in the bristled part is not flat. 
 
     
     
       13. The method according to  claim 12 ,
 wherein the brush surface has irregularities. 
 
     
     
       14. The method according to  claim 13 ,
 wherein the brush surface has irregularities in both the length direction and the width direction of the bristled part. 
 
     
     
       15. The method according to  claim 1 ,
 wherein the bristles are fused to the bristle base of the brush main body by an in-mold process or fused-in process. 
 
     
     
       16. The method according to  claim 1 ,
 wherein, in the process (c), in a state that a cutting plate is overlapped at a cavity side of a first mold member, inserting a tuft comprising a plurality of the bristles into tuft insertion holes formed in a cutting plate and tufts holding holes formed in the first mold member from end side of the bristles against an opposite side from a cavity side, then bringing a free end portion of the tufts in contact with a backplate, setting a brushing surface formed by end portions of the bristles at a predetermined shape, cutting a base portion of the tufts along the cutting plate, then removing the cutting plate, heat melting a base end of the tuft to form a thick portion comprising a fused mass at the base end of the tuft, then mounting the thick portion in such that the tuft is fusion-bonded to a bristle base, and forming a brush main body made of a synthetic resin with the bristle base in molds. 
 
     
     
       17. The method according to  claim 1 ,
 wherein, in the process (c), in a state that a bristled part cover and a cutting plate are overlapped at a cavity side of a first mold member, inserting a tuft comprising a plurality of the bristles into a tuft hole formed in the bristled part cover, tuft insertion holes formed in a cutting plate and tufts holding holes formed in the first mold member from end side of the bristles against an opposite side from a cavity side, then bringing a free end portion of the tufts in contact with a backplate, setting a brushing surface formed by end portions of the bristles at a predetermined shape, cutting a base portion of the tufts along the cutting plate, then removing the cutting plate, heat melting a base end of the tuft to form a thick portion comprising a fused mass at the base end of the tuft, then mounting the thick portion in such that the tuft and the bristled part cover are fusion-bonded to a bristle base, and forming a brush main body made of a synthetic resin with the bristle base in molds.